etna_viv: Add option to enable profile counters support

Ideally we'd also want to add `viv_gpu_top` to the build somehow, as it is currently the only application using the profile counters, but this is a first step.

I've submitted a similar patch to add Vivante performance counters options to @mth for the linux kernel.

Example viv_gpu_top executable for the gcw can be found here: https://download.visucore.com/gcwzero/viv_gpu_top (built against kernel v4)